libqpe, opie-taskbar: Fix linking errors found with 2.20 ld

libqpe, opie-taskbar: Fix linking errors found with 2.20 ld

* Fix PR #5376

* Dont remove ~LnkProperties when QTOPIA_INTERNAL_FSLP is not defined
  this could cause g++ to emit default destructor which will be inlined
  and as we asked inlines to have hidden visibility it could make the
  destructor hidden in the final library this happens now because ld
  can merge the visibility attributes which it did not do before.

* Note that this fix might be needed in few other places too.
  We will fix them as we encounter them.

* Remove the workaround in opie-taskbar

Signed-off-by: Khem Raj <raj.khem@gmail.com>